Obesity is poised to overtake tobacco as the greatest contributor to preventable death in the United States. Overweight children are at increased risk of being overweight as adults and are at increased risk of high morbidity related to a number of negative health outcomes (e.g., cardiovascular disease, diabetes, some cancers, and stroke). Risk factors for overweight and obesity start in early life, even prenatally although research that examines the longitudinal relationship between early life factors and obesity are sparse. We are particularly limited in our understanding of the influence of early life factors on individual overweight and obesity trajectories spanning over childhood, adolescence and early adulthood given the lack of repeated anthropomorphic measurements in most existing studies. We propose to examine the influence of prenatal and postnatal factors on BMI trajectory among youth transitioning from late childhood and adolescence into early adulthood. Given that obesity in childhood and adolescence increases risk for obesity in adulthood, research aimed at enhancing our understanding of potentially modifiable risk factors for an elevated BMI trajectory is important. To date most obesity research has failed to explore risk factors that explain patterns of BMI trajectory. Using a statistical analysis technique that is able to characterize groups of youth that express differential patterns of BMI over time-General Growth Mixture Modeling-this project will assess the impact of critical periods of exposure on obesity risk. These aims will be investigated using the Growing Up Today Study (GUTS), an ongoing longitudinal cohort study of 9,039 adolescent girls and 7,843 boys (aged 9-14 at baseline in 1996) who are offspring of mothers participating in the Nurses'Health Study II (NHS II). As a result, these datasets also allow for a unique opportunity to explore intergenerational predictors of obesity as well as the intersection of prenatal and postnatal factors, and childhood health behavior in explaining predictors of distinct trajectories of BMI during the transition from childhood to young adulthood. PUBLIC HEALTH RELEVANCE: The proposed study will use longitudinal cohort data (Growing Up Today Study) to investigate the influence of prenatal and postnatal factors on BMI trajectory among youth transitioning from late childhood and adolescence into early adulthood. The chosen outcome occurs with high prevalence in early life and influences a number of negative health outcomes (e.g., cardiovascular disease, diabetes, some cancers, stroke) throughout the life cycle. The central hypothesis is that adverse early life factors have both an independent and a cumulative impact on later weight trajectory but may be modified by lifestyles and behaviors. We will use growth mixture modeling to estimate the pattern of change in BMI across age beginning in late childhood to early adulthood and the relative influence of the pre- and post-natal factors and childhood behavior on the BMI trajectories. This novel analytic technique holds the promise of identifying distinct populations at risk for obesity and targeting critical time periods for long-term obesity prevention that may be unique to each subgroup.